The NATO-led security mission in Afghanistan confirmed the bomb blast and said there were no reports of casualties or injuries.

Afghan police were not able to enter the area, which also hosts the Italian, German and Turkish embassies, as it is under ISAF control. The incident was being investigated by ISAF and Afghan security forces. No one has yet claimed responsibility for the attack.

Within half an hour of that explosion taking place, a small roadside bomb targeting a police district office in Kart-e-Naw, in the south of the capital, exploded but also caused no injuries, Kabul police spokesman Hashmat Stanikzai said.

Earlier in the day, a soldier with the NATO military alliance was killed when insurgents attacked a military base in eastern Afghanistan.

Five militants with light weapons attacked the base in Ghani Khel district, said Ahmad Zia Abdulzai, spokesman for the governor of Nangarhar province.

"They detonated an explosives-laden car at the entrance of the base and then started firing on the guards," Abdulzai said.

He said one of the attackers died in the explosion and four others were gunned down by security guards.

The Taliban claimed responsibility for the attack.

Also, in Khost province, four intelligence agents including a local officer were killed by a roadside bomb late Friday, an official said.